[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [PATCH] X86: Prefer TSC-deadline timer in Xen
Architecturally the TSC Deadline feature comes along with reliable TSC. For hot-add physical CPU case, if original APIC timer & TSC calibration work well, then TSC Deadline should not have problem. Jimmy > -----Original Message----- > From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx] > Sent: Friday, October 29, 2010 6:29 AM > To: Wei, Gang; Keir Fraser; Tim Deegan > Cc: Brown, Len; xen-devel@xxxxxxxxxxxxxxxxxxx; Jan Beulich > Subject: RE: [Xen-devel] [PATCH] X86: Prefer TSC-deadline timer in Xen > > The change to cstate_restore_tsc reminds me... > > TSC should never be written if it is being used to > generate system time, and I think cstate_restore_tsc > is only used on systems where another clocksource > is used to generate system time. (And it generates > a rather poor approximation of TSC.) Are there any > machines where cstate_restore_tsc might get executed > but TSC_Deadline is in use? If so, might there be > a race condition here? Also, are there any > issues with using TSC Deadline on a system with > the potential for hot-add physical CPUs? > > I suspect cstate_restore_tsc doesn't get executed > if TSC is reliable, and the TSC Deadline feature > is probably only available on systems where TSC > is reliable, but am not sure. > > Thanks, > Dan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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